Process for producing 2-hydroxy alkylcarbamic acid esters



United States Patent 3,326,968 PROCESS FOR PRODUCING Z-HYDROXY ALKYL-CARBAMIC ACID ESTERS Leonard Levine and George E. Ham, Lake Jackson,Tex., assignors to The Dow Chemical Company, Midland, Mich., acorporation of Delaware No Drawing. Filed Dec. 9, 1963, Ser. No. 329,2176 'Claims. (Cl. 260-482) may be represented by the following equation 0o C-R II II wherein each R and R is a hydrogen atom or a lower alkylgroup of from 1 to 4 carbon atoms and R is an alkyl group of from 1 to 6carbon atoms. Thus, R and R may each be a methyl, ethyl, n-pro-pyl,i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl group and R may be amethyl, ethyl propyl, butyl, pentyl or hexyl group.

Typical acid reactants include formic, acetic, propionic, butyric andpentanoic acids which may be reacted with C -C alkyll-aziridinylcarboxylates in which the aziridine ring may be substitutedwith up to four lower alkyl groups. Examples of suitablel-aziridinylcarboxylates include methyl aziridinylcarboxylate, ethylZ-n-propyl-l-aziridinylcarboxylate and ethyl2-methyl-l-aziridinylcarboxylate.

The process of the invention is carried out at temperatures of fromabout 15 to 200 C. (preferably from about 25 to 160 C.). Mole ratios ofalkanoic acid to carboxylate of from about 0.5 :1 to 10:1 may be used.It is usually desirable to use an excess of acid because theaziridinylcarboxylates have a tendency to polymerize on heating. A 10 to20 percent molar excess of acid is sufiicient. The process may becarried out at subatmospheric and superatmospheric pressures and isnormally carried out at atmospheric pressure under reflux conditions. Athigher temperattures (170 to 200 C.), pressures greater than atmosphericpressure may be used effectively. An inert solvent may be used in thereaction mixture but is not necessary to carry out the reaction.

The compounds of the invention are useful as inhibitors for retardingthe reaction of a halohydrocarbon (e.g., methyl chloroform,perchloroethene, etc.) with a metal such as aluminum. Concentrations offrom about 3 to percent by weight of the carbamate ester in the halo--a1kane are generally sufficient to slow down or stop the reaction. Thecompounds are particularly useful as inhibitors for halohydrocarbonswhich are used as commercial degreasing solvents for metals.

In addition, the compounds are useful in biological applications. Forexample, solutions or dispersions of ethyl 2-propionyloxyethylcarbamatein concentrations of about 500 parts per million are effective againstthe plum curice culio when contacted with this pest by spraying or othermeans.

The following examples are submitted for the purpose of illustrationonly and are not to be construed as limiting the scope of the inventionin any way.

Example I To '74 grams (1.0 mole) of propionic acid was added dropwise30 grams (0.26 mole) of ethyl l-aziridinylformate (ethyll-aziridinylcarboxylate) while stirring under a nitrogen atmosphere. Thetemperature was maintained at 15-25 C. during the reaction. The excessacid was neutralized with dilute sodium hydroxide and the mixture wasextracted several times with benzene. The benzene solution was washedwith water, dried over anhydrous calcium sulfate, filtered andconcentrated. Vacuum distillation yielded 28 grams (57 percent oftheory) of crude ethyl ester of Z-hydroxyethylcarbamic acid propionate.The product was redistilled and had the following properties: n =1.4375;boiling point=7677 C. at 0.2 mm. of Hg.

Analysis ('C H NO (ethyl 2-propionyloxyethylcarbamate). Theory: C,50.78; H, 7.99; N, 7.40. Found: C, 50.50; H, 7.97; N, 7.12.

Infrared spectroscopic analysis was consistent with the formula:

The reaction of Example I was repeated at 140156 C. using 19.4 grams(0.262 mole) of propionic acid and 30.0 grams (0.26 mole) of ethyl1aziridinylcarboxylate. Vapor phase chromatographic analysis of thereaction mixture showed that it contained 96 percent (by weight) of theexpected product. Distillation gave a percent yield of:

Example 111 In a manner similar to Example I, 0.2 mole of ethyll-aziridinylcarboxyl-ate was mixed with 12.5 moles of glacial aceticacid at 25 C. This mixture was allowed to stand for 30 minutes afterwhich the excess acid was removed under vacuum and the residue distilledto yield 87 percent of theory of ethyl 2-acetyloxyethylcar-bamate havingthe following properties: =1.4422; boiling point=91-101 C. at 0.1 mm.Hg; density (20 C.): 1.116.

We claim as our invention:

1. A method of preparing carbamate esters having the formula:

wherein:

(a) each R and R is independently selected from the group consisting ofthe hydrogen atom and a lower alkyl group of from 1 to 4 carbon atoms,and

-(b) R is an alkyl group of from 1 to 6 carbon atoms which comprisesreacting at a temperature of from 15 to 200 C. a compound of the formulawherein (a) R is selected from the group consisting of the hydrogen atomand a lower alkyl group of from 1 to 4 carbon atoms, and

(b) R is an alkyl group of from 1 to 6 carbon atoms with an alkanoicacid of from 1 to carbon atoms, the conversion to carbamate ester takingplace in about onehalf hour or less.

2. A method according to claim 1 wherein the reaction is carried out attemperatures of from about 25 to 160 C.

3. The process of claim 2 wherein a 10 to 20 percent molar excess ofcarboxylic acid is used.

4. A process for the manufacture of ethyl Z-propionyloxyethylcarbamatewhich comprises reacting ethyl l-aziridinylcarboxylate with propionicacid at a temperature of from to 200 C., the conversion to ethyl2-propionyloxyethylcarbarnate taking place in about one-half hour orless.

5. A process for the manufacture of ethyl Z-acetyloxyethylcarbamate whiccomprises reacting ethyl l-aziridinylcarboxylate with acetic acid at atemperature of from 15 References Cited UNITED STATES PATENTS 4/1959Tazuma 260-453 12/1959 Reeves et al 260482 X OTHER REFERENCES Jones etal.: J. Org. Chem., vol. 9, pages 500 512 (1944), copy in Sci. Lib. (QD241 J6), relied upon page 503.

LORRAINE A. \VEINBERGER, Primary Examiner.

ALBERT P. HALLUIN, Assistant Examiner.

1. A METHOD OF PREPARING CARBAMATE ESTERS HAVING THE FORMULA: